save

onnx_ir.save(model, path, format=None, external_data=None, size_threshold_bytes=256, max_shard_size_bytes=None, callback=None)

Save an ONNX model to a file.

The model remains unchanged after the call. If any existing external tensor references the provided external_data path, it will be invalidated after the external data is overwritten. To obtain a valid model, use load() to load the newly saved model, or provide a different external data path that is not currently referenced by any tensors in the model.

Tip

A simple progress bar can be implemented by passing a callback function as the following:

import onnx_ir as ir
import tqdm

with tqdm.tqdm() as pbar:
    total_set = False

    def callback(tensor: ir.TensorProtocol, metadata: ir.external_data.CallbackInfo) -> None:
        nonlocal total_set
        if not total_set:
            pbar.total = metadata.total
            total_set = True

        pbar.update()
        pbar.set_description(f"Saving {tensor.name} ({tensor.dtype}, {tensor.shape}) at offset {metadata.offset}")

    ir.save(
        ...,
        callback=callback,
    )
Parameters:

  • model (Model) – The model to save.

  • path (str | PathLike) – The path to save the model to. E.g. “model.onnx”.

  • format (str | None) – The format of the file (e.g. protobuf, textproto, json, etc.). If None, the format is inferred from the file extension.

  • external_data (str | PathLike | None) – The relative path to save external data to. When specified, all initializers in the model will be converted to external data and saved to the specified directory. If None, all tensors will be saved unmodified. That is, if a tensor in the model is already external, it will be saved with the same external information; if the tensor is not external, it will be serialized in the ONNX Proto message.

  • size_threshold_bytes (int) – Save to external data if the tensor size in bytes is larger than this threshold. Effective only when external_data is set.

  • max_shard_size_bytes (int | None) – Maximum cumulative size in bytes for a single external data shard file. When None (the default) all external tensors are written to the single file given by external_data. When set, tensors are distributed across numbered shard files (e.g. model-00001-of-00003.data). Because the ONNX format stores location, offset, and length per tensor, no separate index file is created — the saved ONNX proto itself encodes which shard each tensor lives in. If a single tensor is larger than this value, it is written in its own oversized shard file. Effective only when external_data is set.

  • callback (Callable[[TensorProtocol, CallbackInfo], None] | None) – A callback function that is called for each tensor that is saved to external data for debugging or logging purposes.

Raises:

  • ValueError – If the external data path is an absolute path.

  • ValueError – If max_shard_size_bytes is not greater than 0.

  • ValueError – If max_shard_size_bytes is set without external_data.

  • FileExistsError – When max_shard_size_bytes is set and any destination shard file already exists on disk. The sharded write path never overwrites existing files; delete the conflicting files or choose a different external data path to re-save. The single-file path (max_shard_size_bytes is None) instead overwrites external_data unconditionally and never raises here.

Return type:

None